1. Field of Invention
The present invention relates to an apparatus for extruding liquid, and more particularly, to an extrusion apparatus for high viscosity liquid.
2. Related Art
An extrusion apparatus is required to coat the existing high viscosity liquid, such as glass pastes. The conventional extrusion apparatus comprises a gun body, a retainer set at front end of the gun body, a push rod running through the gun body and a wrench hinged to the gun body. The push rod is shaped as a prism, and could slide within the gun body. A push plate is hinged to the upper end of the wrench, on which a through hole is arranged with a shape similar to the cross section of the push rod. The size of the through hole is slightly larger than that of the cross section of the push rod. An anti-back plate with the same shape as the push plate is further provided after the gun body. The push rod is passed through the anti-back plate. During operation, a cylinder storing high viscosity liquid is fixed on the retainer, the wrench is turned to drive the push plate, the push rod is pressed against a piston in the cylinder, and the piston is further pushed to extrude the liquid out of the cylinder, so that the high viscosity liquid is coated. During operation of the extrusion apparatus, the liquid is extruded by turning the wrench, but the amount of the liquid extruded out of the cylinder is difficult to control, and the uniformity of coating of the liquid is impaired and the coating quality can not be guaranteed. Moreover, if the extrusion apparatus has been operated for a long time, abrasion tends to occur between the push plate and the push rod, and the use effect is further impaired. Furthermore, the anti-back plate is used to prevent the push rod moving reversely in real time. The outlet of the cylinder is generally not too large. After the wrench is turned once, the liquid in the cylinder can not flow out of the outlet in time, and the piston in the cylinder applies a reverse acting force to the push rod. The push rod can not be moved reversely under action of the anti-back plate. This way, there is still liquid flowing out of the outlet after a period of coating, which causes a lot of waste. A large amount of high viscosity liquid is adhered around the outlet, causing the outlet unclean. Once the high viscosity liquid is solidified, the liquid can not conveniently flow out of the cylinder through the outlet.